1. The Field Of The Invention
The present invention relates to an electromagnetic shielded connector and in particular to the shield for use in combination with a standard connector to get a connecting system having electromagnetic compatability.
2. The Prior Art
Electromagnetic compatibility has been a concern in the electrical system design field for some time. Equipment must be designed so that it is neither a source of interference nor susceptible to external interferences. Both filtered connectors and shielded connectors are often required when electromagnetic compatibility is a strong design consideration. Significant work has been done in the past on military equipment to prevent electromagnetic interference by providing both filtered and shielded connectors. Electromagnetic compatibility is becoming of much more concern to equipment being developed for the commercial market place, for example computers. Three factors have contributed to the growing need for electromagnetic compatibility protection in this type of equipment:
(1) electrostatic discharges have been found to be of major concern in commercial computers since this type of discharge can seriously affect the operation of the computer equipment;
(2) ground loops resulting from equipment operating from different power outlets not only can adversely affect equipment operation, but it can also generate a potential safety hazard; and
(3) the Federal Communication Commission has recently amended its rules governing electromagnetic interference emissions from equipment to include computer type systems.
When systems shielding is required for electromagnetic compatibility, connectors must also be shielded since they form an integral part of the total energy transfer link. The design considerations for connectors parallel those for general shielded enclosures. The connector must be surrounded with a metallic barrier with the amount of shielding offered by a particular metal depending upon many factors including thickness, conductivity, permeability, type of field, and the distance from the source to the field. Seams in the connector must be protected from leakage using good RF gasketing techniques. Since good metal to metal contact must be provided along the complete perimeter of the contact, mating surfaces must have surface treatment which will ensure good contact. The interface between the connector and cable shield must be designed to provide good peripherial contact. The separable interface between the plug and receptacle members must be designed to provide good peripherial contact. Also openings in the shell must be kept to a minimum and limited to size to prevent leakage.
Many of the shielded connectors on the market today usually have a heavy body which is cast in either a single piece or a two piece design. If a two piece design is used then a separate gasket is usually provided to seal the resulting seam. Some form of external back shell is then added to provide means for terminating the cable braid to the connector. The back shell usually consists of a number of separate parts resulting in an expensive addition to the connector. The separable connector interface is protected with another gasket which is either supplied separately or attached to one part of the connector. This approach results in a connector system which provides good shielding, however, it is usually expensive, difficult to assemble, and overall rather bulky in size and appearance.
The emerging need for shielded connectors in the commercial marketplace will demand devices which are inexpensive, easy to apply and still provide high levels of shielding effectiveness without being unduly cumbersome in size and configuration.